Investments work out different for different people, so there is no single most beneficial way of investing. Investing in real estate is said to be lucrative, but even this sector slows down sometimes. You can also go into stock trading, but you should talk to a financial advisor for advice.
Investment is related to saving and deferring consumption. Choosing a beneficiary is the cleanest and clearest way of leaving someone money after you're gone. But the process also requires consideration of both the amount of money at stake and the beneficiary's ability to handle a potential windfall.